Tsuga (Endl.) Carr.
Tsuga is a small genus of ca. 10 species, native in the northern hemisphere (but none in Belgium). Two North American species are more or less widely cultivated for timber production or as ornamentals: Tsuga canadensis and T. heterophylla. Both were recently recorded as escapes from cultivation in Belgium.
Leaf margins in Tsuga are often minutely spinulose. However, spinules are usually very inconspicuous and unevenly distributed and almost lack in young leaves of saplings. This character should therefore be checked on adult leaves of the supposed parental plants. In saplings of Tsuga leaves are markedly bicoloured: white stomatal bands on the abaxial surface are very prominent and contrast with the shiny green adaxial surface.
- Leaves gradually narrowed at apex, abaxially with few lines of stomatal bands (5-6) === 1. Tsuga canadensis
- Leaves parallel-sided and very abruptly narrowed at apex, abaxially with 7-8 lines of stomatal bands === 2. T. heterophylla
Christensen K.I. (2000) Coniferopsida. In: Jonsell B. (ed.), Flora Nordica, vol. 1. The Bergius Foundation, Stockholm: 91-115.
De Koning J., Van den Broek J.W., Van de Laar H.J. & Fortgens G. (2000) Nederlandse dendrologie (13e druk). H. Veenman & zonen, Ede: 585 p.
Farjon A. (2001) World checklist and bibliography of conifers. Royal Botanic Gardens, Kew (2nd edition).
Heywood V.H. (ed.) (1964) Pinaceae. In: Tutin T.G. & al. (eds.), Flora Europaea, vol. 1. Cambridge University Press, Cambridge: 29-35.
Lewis J. (1986c) Tsuga. In: Walters S.M. & al. (eds.), The European Garden Flora, vol. 1. Cambridge University Press, Cambridge: 94-95.
Roloff A. & Bärtels A. (2006) Flora der Gehölze (2e Auflage). Ulmer, Stuttgart: 844 p.
Taylor R.J. (1993) Tsuga. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 2. Oxford University Press, New York-Oxford: 362-365.